Japanese encephalitis virus infection case definition - V1.1

This document contains the case definitions for Japanese encephalitis virus infection which is nationally notifiable within Australia. This definition should be used to determine whether a case should be notified.

Under Clinical evidence:A clinically compatible febrile illness of variable severity associated with neurological symptoms ranging from headache to meningitis or encephalitis. The encephalitis cannot be distinguished clinically from other central nervous system infections.
Symptoms may include headache or fever.
Clinical signs may include meningeal signs, stupor, disorientation, coma, tremors, generalised paresis, hypertonia, and loss of coordination.

Replace it with the same text from clinical evidence in West Nile virus/ Kunjin and Murray Valley encephalitis virus case definitions:
1. Non-encephalitic disease: acute febrile illness with headache, myalgia and/or rash
OR
2. Encephalitic disease: acute febrile meningoencephalitis characterised by one or more of the following:

focal neurological disease or clearly impaired level of consciousness

an abnormal computerised tomogram or magnetic resonance image or electroencephalogram

presence of pleocytosis in cerebrospinal fluid

OR3. Asymptomatic disease: case detected as part of a serosurvey should not be notified.

Reporting

Confirmed case

Laboratory definitive evidence

1. Isolation of Japanese encephalitis virus

OR

2. Detection of Japanese encephalitis virus by nucleic acid testing

OR

3.IgG seroconversion or a significant increase in antibody level or a fourfold or greater rise in titre of Japanese encephalitis virus-specific IgG proven by neutralisation or another specific test, with no history of recent Japanese encephalitis vaccination.

OR

4. Detection of Japanese encephalitis virus-specific IgM in cerebrospinal fluid, in the absence of IgM to Murray Valley encephalitis, West Nile/Kunjin and dengue viruses

OR

5. Detection of Japanese encephalitis virus-specific IgM in serum in the absence of IgM to Murray Valley encephalitis, West Nile/Kunjin and dengue viruses, with no history of recent Japanese encephalitis vaccination.
Confirmation of laboratory result by a second arbovirus reference laboratory is required if the case appears to have been acquired in mainland Australia.